This invention relates to the fabrication of fixed partial dentures (bridges) to replace missing teeth in the anterior and posterior areas of the mouth.
Fixed partial dentures have been fabricated from a wide variety of materials including ceramics, metals, plastics, and combinations of those materials. For example, bridges have been formed having an all metal construction, an all ceramic body (aluminous porcelain, spinel ceramics), a laminate of porcelain fused onto metal, and a laminate of acrylic bonded to metal. Each of those constructions exhibits certain advantages and is subject to inherent disadvantages. Nevertheless, one problem which has plagued all of those materials has involved fitting of the prosthesis in a patient's mouth.
In general, fixed partial dentures have comprised at least three parts, viz., two abutment crowns and a pontic therebetween. In fabricating a bridge, an impression is made of the area in the patient's mouth, a cast is prepared, and a dental technician then fashions a bridge therefrom. Where metal materials are employed, the three parts may be formed as an integral unit or the parts soldered or otherwise joined into a single unit. Where ceramic materials are involved, the components are typically assembled at the dental laboratory and delivered to the dentist as a single unit. A low temperature fusing solder glass ( a dental porcelain) or other sealing means is used to surround the other aluminous porcelain or other ceramic components.
Because the impression and/or die prepared therefrom may not exactly represent the precise location of the abutment teeth and/or because the abutment teeth may move between the time the impression is made and the finished bridge is fitted in the patient's mouth, often the appliance will not fit properly. Thus, the customary mode of attachment has involved simple butt sealing or, occasionally, sealing by means of a dovetail or tongue-and-groove configuration. Such forms of attachment do not permit adjustments in the overall geometry of a appliance or in the profile of the individual parts to be quickly and readily performed. Accordingly, when the dentist notes inaccuracies in the fitting to the abutment teeth in the patient's mouth, the common practice is to return the bridge to the dental technician for the necessary alterations. Not infrequently, the metal appliance frame must be separated, the required adjustments made, and the parts re-soldered. As can be appreciated, those circumstances demand at least one further visit by the patient to the dentist's office to insure proper fitting.
Fixed partial dentures have been fabricated which have been asserted by their designers as permitting greater precision in fit to be achieved. For example, a dovetail or tongue-and-groove attachment has been designed wherein the joint is not permanently sealed together, thereby permitting vertical movement in the joint but lateral motion is constrained. Other types of precision attachments have been fashioned but none of the designs thereof has permitted sufficient omni-directional movement of contiguous appliance parts to be of any significant use in making adjustments.
Therefore, the principal objective of the present invention was to design a means for attaching the parts of a fixed partial denture together which permits adjustments to be made quickly and readily, thereby insuring proper fitting of the bridge in a single visit by the patient to the dentist's office.